UPSERT Order processing preferences

When a Quickbase server gets a large UPSERT via API, how does the server perform the process/calculation to locate the correct Record ID# and determine whether to update/add the record in the table?

Does the Quickbase system have a preference for the order of records? 

I'm thinking about what uses more processing in terms of an UPSERT. When I API a bulk UPSERT to a QB table leveraging a UNIQUE field (not the Record ID#) what is the preferred sort order of the records UPSERTED?

I can sort using the UNIQUE field.

I can sort using Record ID#.

I can not sort.

Wonder if anyone at Quickbase has performed this type of test and measured the performance?